1. Field of the Invention
This invention relates to a vane pump, and in particular a vane pump that is suitable as an oil pressure source for a power steering device of an automotive vehicle.
2. Description of the Related Art
As is generally known, there have been proposed vane pumps for a power-steering system of an automotive vehicle. The vane pump typically includes a rotor placed in a cam ring that is received in a pump housing. Plural vanes are slidably provided in corresponding slots formed in the rotor, and a pair of wall members are provided to close both side surfaces of the cam ring. By this arrangement, a pump operation is performed with a rotation of the rotor as a top portion of each vane, and both side surfaces of each vane touch an inner surface of the cam ring, and surfaces of the wall members facing the vane, respectively. This type of apparatus is disclosed in, for example, Japan Utility Model Publication (koukai) No. 6-14481, and Japan Patent Publication (koukai) No. 10-184563.
As shown in FIG. 18 illustrating one conventional design, oil is supplied from an oil intake passage 101 to an intake port. An intake chamber 102 provided with a concave-shaped groove in its cross section is formed on a rear housing 104 that faces a cam ring 103 in an axial direction of the cam ring 103. The intake chamber 102 is arranged at an outer portion of the cam ring 103 in a radial direction of the cam ring 103 to avoid an interference with the cam ring 103. Thus, a size of the vane pump in the radial direction of the cam ring 103 is expanded, when the intake chamber 102 that has a large cross sectional area is formed for the purpose of increasing an induction efficiency. However, since it is undesirable that the size of the vane pump becomes large in view of downsizing, there is a difficulty in providing a compact vane pump that has an intake chamber 102 with a large cross section area. Therefore, it has been difficult to increase the induction efficiency. While the area of the intake chamber 102 can be enlarged by expanding the intake chamber 102 in the axial direction of the cam ring 103, since the intake chamber 102 is provided with a flat shape cross section, a strong flow resistance results that would cause a decrease of the induction efficiency.
As shown in FIG. 19 illustrating another conventional design, a fluid chamber 202 is formed inside of a housing member 201, and receives a pressure plate 203, a cam ring 204, and a thrust plate 205. The pressure plate 203 and the thrust plate 205 are arranged for closing both sides of the cam ring 204. The fluid chamber 202 is formed into a cylindrical shape. A low-pressure fluid passage 206, which constitutes an intake passage, is formed on an inner surface of the fluid chamber 202 that faces an outer surface of the cam ring 204. The low-pressure fluid passage 206 is provided with a concave-shaped groove in its cross section. However, since the low-pressure fluid passage 206 is located at an outside of the cam ring 204 with respect to a diameter of the cam ring 204, it is difficult to provide the low-pressure fluid passage 206 that has a large cross sectional area, keeping the compactness. Therefore, the area of the low-pressure fluid passage 206 cannot be enlarged enough.
Accordingly, in view of above-described problems encountered in the related art, a principal object of the present invention is to provide a vane pump that has an intake passage with a large cross sectional area.
Another object of the present invention is to provide a vane pump that is compact.
Still another object of the present invention is to provide a vane pump that is easy to assemble.
In order to achieve these and other objects, there is provided a vane pump that comprises a pump housing that includes an inlet, an outlet, and therein a hollow space, a cam ring received in the hollow space, and a rotor placed in the cam ring. The rotor defines a rotation axis and comprises plural vanes arranged in corresponding slots formed in the rotor with a slidable contact in a radial direction of the rotor. A first wall member is received in the hollow space, with one side of the first wall member facing one side of the cam ring, the first wall member comprising an intake passage provided with a groove that is formed so that a partition wall portion is defined between the intake passage and an interface between the first wall member and the cam ring. A pair of intake ports are formed on the one side of the wall member, and each intake port is connected with the inlet by the intake passage. A pair of outlet ports are formed on the one side of the first wall member.